Normandy Day Trip

My recommendation would be that you try to book the special one-day tour Overlord runs (I do not know how frequently) for people coming up from Paris by train. The tour begins at the Bayeux train station (rather than in the historic center) just a bit later than the standard tour. The endpoint of the tour is the train station, making it easy for you to return to Paris in the evening. Doing this gets you much more actual time at the invasion sites than you'll have if you travel by bus from Paris to Normandy (it's at least 3 hours just to Bayeux; the beaches are beyond Bayeux).

If the schedule for the special Ovelord tour doesn't work for you, I'd recommend checking on the size of the vehicles used for the Paris-based tours. Most if not all the Bayeux companies use vans. I wouldn't want to take a tour from Paris in a 40-passenger bus. There would be considerable time wasted as all those people climbed off and back on the bus at each stop.

Live would be easier if you could spend one night in Bayeux and take the tour the next day.

I agree with this advice--take the train to Bayeux and then join a local tour that picks you up at the train station. If Overlord is booked up, there are other companies in Bayeux that offer the same service. Also, the Caen Memorial Musuem offers a similar tour that starts at the Caen train station, see https://normandy.memorial-caen.com/your-visit/your-own-family-or-friends/day-trips. By taking the train on your own from Paris, you will save about an hour of travel time each way, compared to a bus tour that starts in Paris. That gives you more time at the sites and less time traveling.

I agree with the others - the Overlord tour is great. My mother and I took it in October.

https://www.overlordtour.com/product/tour-2fs-omaha-utah-full-day-tour-week-days-only/

Our guide was Thomas and we had such an amazing day.

We took the 7:05am direct train from Paris St. Lazare which arrived at the Bayeaux station about 9:20am where we were greeted by Thomas. There were 6 people total - another mother/daughter and a husband/wife - plus Thomas in a 9 passenger van so we were extremely comfortable and the small group size makes it very personal. We had a break for lunch on our own in Sainte Mere Eglise and were able to spend time exploring Bayeaux before boarding our 6:30pm return train to Paris.

It was a long, but easy and enjoyable day!

Lesley's post reminded me that the stop at St-Mere-Eglise is just about long enough for a quickish sit-down lunch or for a non-dawdling visit to the Airborne Museum. There is definitely not time for both. I chose to buy a sandwich at a bakery pointed out by the driver and wolf it down while sitting on a bench, then I trotted off to the museum. Knowing what I do now, I'd try to find something to take with me for lunch to save a few more minutes for the museum. Note that you may not eat in the vehicle.